Silver halide photographic materials have a tendency to experience fogging on account of the presence of nuclei that develop in the absence of exposure. Fogging that occurs during storage is in most cases prone to have adverse effects on photographic materials such as a decreased sensitivity and deteriorated gradation.
In order to minimize these undesirable effects, the addition of antifoggants or stabilizers to silver halide emulsions has been proposed. For example, U.S. Pat. Nos. 2,403,927 and 3,804,633 and Japanese Patent Publication No. 2825/1964 show the use of 1-phenyl-5-mercaptotetrazoles or 4-hydroxy-6-methyl-1,3,3a,7-tetrazaindene as fog restrainers. However, these compounds are not completely satisfactory in their ability to inhibit fogging during storage of photographic materials. They have the additional disadvantage of decreasing the sensitivity of the photographic material or deteriorating its gradation. If fog restrainers are incorporated in color photographic materials with a view to improving their storage stability, the adsorption of the restrainers on silver halide emulsions is so strong as to cause undesirable phenomena such as impairing the spectral sensitivity of the material or retarding silver removal during development. These adverse effects are pronounced in high-sensitivity photographic materials having high silver iodide contents and there has existed a strong need to develop a method that is capable of eliminating them.